AngularJS + ASP.NET Web API Cross-Domain Issue

You can skip the preflight option request by using content-type : application/x-www-form-urlencoded.

AngularJS:

var user = {
   ID: 1,
   Name: 'test'
};

$http({
  url: "api.localhost/api/users/addUser",
  method: "POST",
  data: $.param(user),
  headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
  withCredentials: true,
  }).success(function (data, status, headers, config) {
     console.log(data);
})

Web api:

[HttpPost]
public string AddUser(User user)
{
    // Do something
    return user.Name + " added";
}

Web.config

    <system.webServer>
        <validation validateIntegratedModeConfiguration="false" />
            <handlers>
                <remove name="ExtensionlessUrlHandler-ISAPI-4.0_32bit" />
                <remove name="ExtensionlessUrlHandler-ISAPI-4.0_64bit" />
                <remove name="ExtensionlessUrlHandler-Integrated-4.0" />
                <remove name="OPTIONSVerbHandler" />
                <remove name="TRACEVerbHandler" />

                <add name="ExtensionlessUrlHandler-ISAPI-4.0_32bit" path="*." verb="GET,HEAD,POST,DEBUG,PUT,DELETE,PATCH,OPTIONS" modules="IsapiModule" scriptProcessor="%windir%\Microsoft.NET\Framework\v4.0.30319\aspnet_isapi.dll" preCondition="classicMode,runtimeVersionv4.0,bitness32" responseBufferLimit="0" />
                <add name="ExtensionlessUrlHandler-ISAPI-4.0_64bit" path="*." verb="GET,HEAD,POST,DEBUG,PUT,DELETE,PATCH,OPTIONS" modules="IsapiModule" scriptProcessor="%windir%\Microsoft.NET\Framework64\v4.0.30319\aspnet_isapi.dll" preCondition="classicMode,runtimeVersionv4.0,bitness64" responseBufferLimit="0" />
                <add name="ExtensionlessUrlHandler-Integrated-4.0" path="*." verb="*" type="System.Web.Handlers.TransferRequestHandler" preCondition="integratedMode,runtimeVersionv4.0" />
            </handlers>
            <httpProtocol>
                <customHeaders>
                    <add name="Access-Control-Allow-Origin" value="http://localhost" />
                    <add name="Access-Control-Allow-Headers" value="Origin, X-Requested-With, Content-Type, Accept, Cache-Control" />
                    <add name="Access-Control-Allow-Credentials" value="true" />
                    <add name="Access-Control-Allow-Methods" value="GET, POST, PUT, DELETE, OPTIONS" />
                </customHeaders>
            </httpProtocol>
      </system.webServer>

While stumbling onto this issue with AngularJS 1.3 with Microsoft Web API 2 I found a simple solution to the CORS configuration issue.

• First from Nuget intall - Microsoft WebApi Cors

  Install-Package Microsoft.AspNet.WebApi.Cors
  

• Then in your WebApiConfig.cs file:

  var cors = new System.Web.Http.Cors.EnableCorsAttribute("www.my-angular-web-site.com", "*", "*");
  
  config.EnableCors(cors);
  

You can also enable CORS everywhere with a * instead of your web site but that defeats the purpose of CORS and opens up security holes - but you can do it for testing.

The WebApi.Cors assembly also lets you enable cors controller by controller or with other more granular details. Other details can be found here on the Web API site.

Check out Thinktecture Cors objects, with those (nugettable) you can get full CORS support in WebApi without any code of your own.

Even with a correct CORS implementation I've had a really strange issue with IIS 7 that was solved by enabling all verbs for WebDav (yes, WebDav - don't ask me why I just followed instructions on a blog post :-D).

Do this:

• Open IIS manager, go to your application's Handler Mapping.
• Double click the WebDav handler
• Click "Request Restriction"
• On the "Verbs" tab, select "All verbs".

Again, no idea why WebApi uses WebDav, but this solved problems with POST and DELETE that wouldn't work in spite of a correct CORS implementation.